聚氨酯改性沥青研究现状及发展趋势

Since the emergence of polymer modified asphalt materials, its function and preparation technology have been continuously optimized, the polymer modified asphalt have achieved remarkable results in improving the traffic comfort and prolonging the service life of asphalt pavement. Although polymer modified asphalt have been developed for nearly 100 years, the production, storage and performance of traditional polymer modified asphalt are still unsatisfactory. Therefore, it is urgent to find a new asphalt modifier which can effectively make up for the deficiencies mentioned above. Polyurethane began to implement large-scale industrial production in the late 1960s, and it has been widely used in coating, sealant, elastomer and other fields all over the world. Based on the outstanding advantages in structural, polyurethane is obviously different from other polymer modifiers used in the market. Unfortunately, few studies have been reported on the application of polyurethane in asphalt modification, how to fully explore its advantages and make use of it, so as to meet the current urgent requirement for high-performance asphalt pavement, which has become a major challenge to road workers. In recent ten years, the researchers at home and abroad have focused on the preparation process optimization of polyurethane modified asphalt and its mixture proportion design, and some achievements have been made, but the relationship between the microscopic structure of asphalt and the macroscopic performance of asphalt has not been investigated. Since 2016, some researchers have started to explore the modification of asphalt by using biological polyurethane or thermoplastic regenerated polyurethane, the road performance of it need to be further verified. It's worth noticing that, not all kinds of asphalt can use the same polymer modifier and preparation process to achieve the same modification effect. The modification effect of polymer modifier is not only related to the composition of asphalt, but affected by the amount of modifier added. Additionally, there is a lack of a systematic and scientific evaluation system for polyurethane modified asphalt. Until now, the research results can be summarized as follows. (i) Isocyanates can effectively improve the hardness and elasticity of asphalt; (ii) polyurethane can be combined with traditional polymer modifier or nanomaterials to modify polyurethane modified asphalt, which was prepared by shear method, and then the shear time and shear rate show little influence on the performance of modified asphalt, and the shear temperature perform great influence on the high and low temperature performance and elastic recovery of modified asphalt; (iii) the reasons of good compatibility and mechanical properties of polyurethane modified asphalt were explained from macroscopic properties and microscopic properties, (iv) the particle size of polyurethane modifier has important influence on emulsification and foaming degree of asphalt; (v) in the optimization design of asphalt mixture, it was found that road performance of polyurethane modified asphalt mixture far exceed the technical requirements specified in the specification, except water stability; (vi) the creep flexibility of castor oil-based polyurethane modified asphalt decreased significantly compared with that of matrix asphalt, and the addition of modifier played a toughening and strengthening role. The properties of asphalt can be improved by using biologic polyurethane and thermoplastic polyurethane regenerated materials. This review mainly summarizes a retrospection of the research efforts with respect to the polyurethane modified asphalt, including the characte-ristics of polyurethane, the selection of polyurethane modifier, the modification mechanism of polyurethane modified asphalt, the rheological and microscopic properties of polyurethane modified asphalt, practical use of polyurethane modified asphalt is reviewed from waterproofing enginee-ring, road engineering, biomaterials and recycling. Finally, the existing problems in the present research are put forward, also, the future deve-lopment of polyurethane modified asphalt is presented.